uBlock Origin: developer.chrome.com##+js(trusted-set-cookie, devsite-appearance-cookie, device)
This will require you to add "user-" to your trusted prefixes in the advances settings.
AdGuard: developer.chrome.com#%#//scriptlet('trusted-set-cookie', 'devsite-appearance-cookie', 'device')
AdGuard always trusts user filters.
This for some reason defaults to light instead of device and is a session cookie so it's wiped every time. fuck you too google. by the way google is the one who came up with the prefers-color-scheme CSS media queries and they refuse to use them anywhere except YouTube.